Lithium hydroxide, monohydrate → (RS)-4-[2-(N-ethyl-4,4-dimethyl-1,2,3,4-tetrahydroquinolin-6-yl)-heptyloxy]-benzoic Acid

Participants

Reaction Conditions

Reaction Steps

1 g of (RS)-2-(N-ethyl-4,4-dimethyl-1,2,3,4-tetrahydroquinolin-6-yl)-heptanol dissolved in 20 ml THF were treated with 950 mg of triphenylphosphine, 550 mg of methyl 4-hydroxybenzoate and 0.57 ml of diethyl azodicarboxylate. The reaction mixture was heated to reflux for 6 hours. The mixture was diluted with 100 ml of ether and washed with two portions of 25 ml of water and one portion of 25 ml of sat. aq. sodium chloride solution. The organic phase was dried over MgSO4. The solvents were removed in vacuo and the resulting yellow oil was purified by flash chromatography (SiO2, 3% ethyl acetate/hexanes), giving 670 mg (RS)-methyl 4-[2-(N-ethyl-4,4-dimethyl-1,2,3,4-tetrahydroquinolin-6-yl)-heptyloxy]-benzoate as a pale yellow oil. The ester (670 mg), dissolved in 5 ml THF/5 ml H2O/5 ml methanol, was treated with 260 mg of lithium hydroxide hydrate. The mixture was stirred at 40° C. for 6 hours. The mixture was diluted with 5 ml water and acidified to pH 2 with 1N hydrochloric. The resulting suspension was taken in 20 ml ether and the phases were separated. The aqueous phase was extracted with three portions of 10 ml ether. The combined extracts were dried over MgSO4. The solvent was removed in vacuo and the crude product was purified by preparative tlc (10% methanol/methylene chloride), yielding 320 mg of a pale yellow oil. 1H NMR (CDCl3): 8.01 (d, J=9.0 HZ, 2H), 6.98 (d, J=2.1 Hz, 1H), 6.95-6.85 (m, 3H), 6.52 (d, J=8.4 Hz, 1H), 4.64 (quint, J=5.8 Hz, 1H), 3.32 (q, J=7.1 Hz, 2H), 3.25-3.15 (m, 2H), 2.88 (dd, J=14.1, 5.9 Hz, 1H), 2.78 (dd, J=14.1, 5.9 Hz, 1H), 1.80-1.65 (m, 4H), 1.55-1.25 (m, 6H), 1.24 (s, 3H), 1.18 (s, 3H), 1.11 (t, J=7.1 Hz, 3H), 0.86 (t, J=6.7 Hz, 3H).

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